Tubular metallic bats, including those used for baseball, are known in the art. Such bats typically have a barrel portion that tapers down to a narrow handle. A familiar example is a tubular aluminum bat. Such bats have the advantage of generally good impact response, meaning the bat effectively transfers energy to a batted ball. This effective energy transfer results in ball players achieving good "slugging" distances with batted balls. Those who are familiar with the art commonly refer to bats that allow the hitter to achieve good slugging distances as "lively" bats.
Although today's aluminum bats perform well, there is a continuing quest for more lively bats. Accordingly, one important need is to optimize the impact response of a bat. This quest has produced tubular bats using other materials, such as titanium. Titanium bats perform well, but the material cost and difficulty of working titanium result in a high consumer cost.
In many metallic bats, a knob attaches to the handle end of the bat and an end plug fits into the barrel end of the bat. End plugs have served a variety of purposes in the attempt to achieve a more lively bat. End plugs have operated as structural members to keep bats circular when forces act on the bat, such as when hitting a ball. End plugs also have been used to shift the center of mass to reduce the bat's moment of inertia, allowing greater bat speed, or move the center of mass closer to the optimum impact area of the barrel portion. Other end plugs have added weight to the end of the barrel portion to increase the moment of inertia.
Prior end plugs have not provided sufficient structural support in bat applications where large forces are produced within the bat, such as baseball bats and fast pitch softball bats. Many such end plugs are made entirely of resilient material. As a result, when bats having such end plugs are impacted near the end of the bat, the bats are allowed to deflect sufficiently to permanently deform the bat.
Some prior bats have included metallic tubular inserts in the barrel portion to optimize the recovery of the bat in the area of the insert. U.S. Pat. No. 5,415,398 by Eggiman discloses an insert suspended within the barrel end of the bat. The end of the bat is crimped inwardly to hold the insert in place within the barrel portion. The insert disclosed by Eggiman was a significant advancement in the art. However, with such inserts, slight manufacturing variations in the insert or the frame may change the longitudinal position of the insert. This is especially true of bats, such as baseball bats, that are tapered along the barrel portion. If the longitudinal position of the insert is farther out of the barrel portion than is specified by the design, the barrel portion receives less support from the insert and is more prone to plastic deformation (such as dents). Moreover, if the insert is positioned farther within the barrel portion than is specified by the design, the fit between the crimped end and the insert may not be sufficiently tight.